| 摘要 |
An electric power steering apparatus transmits rotational force of a motor to a rack shaft via a driver pulley, a belt, a driven pulley, and a ball nut. A ball bearing and the driven pulley are fitted to the outer circumferential surface of the ball nut. Also, the ball nut is rotationally supported to the inner circumferential surface of a housing via the ball bearing. A female thread portion is formed on the inner circumferential surface of the driven pulley. The ball nut has a male thread portion formed in a first end and a flange formed in a second end. By fastening the male thread portion and the female thread portion to each other, the ball bearing is clamped between the flange and the driven pulley, while the ball nut and the driven pulley are fastened to each other. |
| 主权项 |
1. An electric power steering apparatus that uses rotational force of a motor to assist motion of a rack shaft, which moves linearly in accordance with a steering operation, the apparatus comprising:
a power conversion mechanism that converts rotation of the motor to linear motion of the rack shaft; and a housing that accommodates the rack shaft and the power conversion mechanism, wherein: the power conversion mechanism includes a ball screw mechanism and a transmission mechanism, the ball screw mechanism includes a ball nut that is threaded to the rack shaft via a plurality of balls and is rotationally supported on an inner circumferential surface of the housing via a bearing, the transmission mechanism includes (i) a driving wheel that rotates as a drive of the motor, (ii) a driven wheel that is formed into a cylindrical shape, has an outer circumferential surface and an inner circumferential surface on which a female thread portion is formed, and is fitted about an outer circumferential surface of the ball nut to transmit rotation of the driving wheel to the ball nut, and (iii) a rotation transmitting member that is located on the outer circumferential surface of the driven wheel and that is capable of transmitting the rotation of the driving wheel to the driven wheel, the ball nut includes a first end in which is formed a male thread portion and that is inserted in and directly coupled to the driven wheel by fastening the male thread portion to the female thread portion of the driven wheel, and a second end where a flange is formed on the outer circumferential surface of the ball nut, an inner race of the bearing being pressed by the flange toward the driven wheel in the axial direction of the ball nut so as to be clamped between the driven wheel and the flange, and a virtual plane perpendicular to the axial direction of the ball nut intersects both the female thread portion of the driven wheel and the portion of the rotation transmitting member that is located on the outer circumferential surface of the driven wheel. |
